Hydrogen is the first element in the periodic table. It is the simplest possible atom composed of one proton in the nucleus which is orbited by a single electron. Hydrogen is the lightest of the elements and is the most abundant element in the universe.

Characteristics and Properties

At standard temperature and pressure hydrogen is a colorless, odorless, and tasteless gas.

Hydrogen is very flammable and burns with an invisible flame. It burns when it comes into contact with oxygen. The byproduct of a hydrogen and oxygen explosion is water or H2 O.

Hydrogen gas is made up of diatomic molecules designated as H2.

Where is hydrogen found on earth?

The most common place to find hydrogen on earth is in water. Each water molecule (H2 O) contains two hydrogen atoms. Hydrogen is also found in a wide range of compounds throughout the earth including hydrocarbons, acids, and hydroxides.

There is very little free hydrogen in the Earth's atmosphere because it is so light that it eventually escapes into space. The only free hydrogen on earth is deep underground.

Stars and Planets

Hydrogen is found mostly in stars and gas giant planets. The Sun is made up of mostly hydrogen. Deep inside stars, the pressure is so high that hydrogen atoms are converted to helium atoms. This conversion is called fusion and it releases heat and energy that we see as sunlight.

How is hydrogen used today?

Hydrogen is a very useful element. It is used to make ammonia for fertilizers, refining metals, and methanol for making artificial material like plastics.

Hydrogen is also used as a rocket fuel where liquid hydrogen is combined with liquid oxygen to produce a powerful explosion. Scientists hope that someday hydrogen can be used as a clean fuel alternative to gasoline.

How was it discovered?

English scientist Henry Cavendish discovered hydrogen as an element in 1766. Cavendish ran an experiment using zinc and hydrochloric acid. He discovered hydrogen and also found that it produced water when it burned.

Where did hydrogen get its name?

The name hydrogen comes from the Greek words "hydro" (meaning water) and "genes" (meaning creator). It was named by French chemist Antoine Lavoisier because when it burns it "creates water".

Ions and Isotopes

Hydrogen can take a negative charge and be an anion called a hydride. It can also take a positive charge as a cation.

Protium is the most common isotope of hydrogen. It has no neutrons and a single proton. Other common isotopes include deuterium and tritium.

Interesting Facts about Hydrogen

Scientists estimate that Hydrogen makes up over 90 percent of all the atoms in the universe.

It is the only element that can exist without neutrons.

Hydrogen becomes a liquid at very low temperature and high pressure. Under extremely high pressure it can become a liquid metal. It is thought that metallic hydrogen exists at the cores of gas giant planets like Jupiter.

Around 10 percent of the mass of the human body is hydrogen.

Because it is so light, it was once used in lighter-than-air-balloons. However, it became too dangerous because of its highly flammable nature.

Hydrogen gas can be produced in a lab by combining a dilute acid with a metal.